From: Joseph S. Myers
The internals manual is where what documentation there is of the front
endinterface (with some documentation of trees) presently is and where
thingsshould link into. It isn't presently wonderfully coherent in structurebut
given the documentation written in some chapters of the manual, theycan always
be reordered later as necessary to give a better-definedstructure. (My old
outline of a possible structure for the front-endinterface parts of the
internals manual is at<http://gcc.gnu.org/ml/gcc/2001-06/msg00125.html>. I
wrote a few bits ofthis for sourcebuild.texi but the bulk of the front-end
interface isundocumented. I'm not asking for you to write all of this, just
todocument all the new and different front-end interfaces on tree-ssa.)

There is no global overview of tree-ssa. The "main page" of the
documentation is empty, and there is no single place that describes
what tree-ssa is and what the overall structure is.
The most useful piece of high-level info is in the proceedings of
the 2003 GCC Summit, page 171-195, but I agree with Richard Kenner that
most of this information should be contained in the various files that
make up tree-ssa.
Unfortunately, the referenced information is in PDF format, so I cannot
easily cut and paste some of it to illustrate my point.
-Geert

Documentation for -ftree-loop-optimize, as well as the switch itself, needs to be removed from the
branch before merge.
The switch only has meaning on the lno-branch.
The switch + docs was added, then it was decided that the loop stuff should go to lno-branch, and
nobody removed the switch again.

Here are additional comments after reading the GCC Internals manual from the tree-ssa branch.
Although Chapter 7 describes the high-level process of going from language-specific trees to GENERIC,
then lowering to GIMPLE and finally going through the various SSA and non-SSA passes
is described in sufficient detail, there is no information on the GENERIC and GIMPLE representations
themselves.
Chapter 8 describes C and C++ front end specific trees, but there is a complete disconnect with tree-
ssa. This chapter needs to be changed to reflect the situation in the tree-ssa branch.
Chapter 9, which deals with analysis and optimization of GIMPLE trees starts with a small introduction
that refers to "the chapter describing GENERIC and GIMPLE" for more details. Such a chapter is much
needed, especially since one of the stated goals of tree-ssa is to improve maintainability.
-Geert

tree-ssa documentation still missing after the mainline merge:
The autoconf and automake versions for the new libbanshee, libgfortran
and libmudflap directories aren't documented in install.texi, but
aren't all the defaults given there for unlisted directories either.
Some also add new versions that weren't previously in the list of those
used.
The new configure options --enable-tree-browser and --with-libbanshee
aren't documented in install.texi.
The options -ftree-combine-temps -ftree-dse -ftree-loop-optimize
-ftree-points-to aren't documented in invoke.texi. Other -ftree-*
options are documented but without use of @opindex to create index
entries.

libgfortran also has an undocumented --enable-cmath configure option.
All configure options should be documented in install.texi; a poor
second-best save maybe for options only of use to GCC developers
is linking from there to separate documentation of a library's options.